The invention relates to water-dispersible blocked polyisocyanates containing ionic groups and polyether groups, a method of manufacturing using a final blocking step, and use of the blocked polyisocyanates to produce textile aids, for example, for water-proofing and oil-proofing or for preparing highly upgraded textiles.
Blocked polyisocyanates containing incorporated polyalkylene oxide units and/or ionic groups are hydrophilic and therefore dispersible in water and can be processed starting from the aqueous phase. These blocked polyisocyanates are thermosetting, since the blocking agent is given off when the deblocking temperature is reached, yielding free isocyanate groups which can react with isocyanate-reactive compounds (that is, compounds containing active hydrogen atoms). These water-dispersible blocked polyisocyanates are suitable not only as lacquer binder components for coating metals, wood, paper, or surfaces of plastic articles, but also as components of aqueous textile finishing agents. Blocked polyisocyanates preferred for this purpose contain incorporated polyalkylene oxide units and ionic groups. Suitable starting components for introducing these hydrophilic groups comprise on the one hand polyether diols and on the other hand compounds that (1) contain groups capable of reacting with isocyanate groups and (2) contain ionic groups or groups convertible into ionic groups. Sulfonate diols, dihydroxycarboxylic acids, and diaminocarboxylic acids are examples of starting components for introducing "potentially" ionic groups.
In the known methods for manufacturing water-dispersible blocked polyisocyanates, polyether diols suitable as hydrophilic components have been incorporated during or after the blocking action, but the reaction with the compounds that provide the ionic groups (except for alkali-metal sulfites, which serve the double purpose of blocking agents and introducing ionic groups) has been brought about with partially blocked polyisocyanates; German Offenlegungsschriften 2,456,469 (believed to correspond to U.S. Pat. No. 4,098,933) and 2,853,937. Alkali-metal bisulfites occupy a special position as inorganic blocking agents. Although these compounds introduce ionic groups, in the past they have been viewed exclusively as isocyanate blocking agents because the ionic groups introduced into the polyisocyanate using alkali-metal bisulfites in the reaction between bisulfite-blocked isocyanate groups and isocyanate-reactive compound are not a component of the polyisocyanate addition products.
It has now unexpectedly been found that technically superior products are obtained, if, in the manufacture of blocked isocyanates containing incorporated polyalkylene oxide units and ionic groups, either a polyisocyanate containing polyalkylene oxide units and ionic groups is produced without using blocking agents, after which the remaining free isocyanate groups of this intermediate are blocked, or alkali-metal bisulfites are used as the blocking agent.
The average molecular weights referred to below are number average molecular weights.